Pyrophoric flints



'UnitedA States Patent PYROPHORIC FLINTS Walter Bungardt, Essen-Bredeney, Germany, assignor, by mesne assignments, to New Process Metals, Inc., Newark, NJ.

Application May 11, 1954, serial No. 429,081

Claims priority, application Germany May 11, 1953 3 Claims. (Cl. 29-19L4) This invention relates to pyrophoric liint of reduced `specific gravity and to a method of preparing the same and i-s a continuation-impart of my prior application Serial No. 381,738, iled September 22, 1953, now U.S. Patent 2,762,707, patented September 11, 1956. More particularly, it relates to an extruded pyrophoric flint of reduced specific gravity and to 'a method of reducing the specificgravity of such liints without substantially aifecting the pyrophorosity and durability of said iiints.

Pyrophoric flints may advantageously be prepared from alloys of cerium and iron. As the'source of cerium, there may be employed mixtures of cerium with other rare earth elements, eg., misch metal, comprising la predominant amount of cerium in admixture with lanthanum, neodymium, and other rare earth elements, such as praseodymium, samarium, etc.

In the production of cast flints from misch metal-iron alloys having a predominant misch metal content, it is customary for the purpose of reducing the specilic gravity, to employ fillers consisting mainly of alloying components of light metals such as magnesium and/ or aluminium. These iillers can be incorporated only in small amounts, e.g., up to 5%, since greater amounts have the effect of making the ilint brittle. Such fillers also reduce the pyrophoric properties of the alloy.

In order to reduce the specific gravity of flints, processes have also been proposed in which the actual carrier of the pyrophoric property, viz., the cerium-iron alloy, is embedded in the form of fine lumps in a synthetic plastic mass.

Flint-s produced in this manner with the aid of plastic binders, however, wear rapidly so that the number of ignitions which they yield, eg., in a pocket lighter, is less than the number obtained with compact, cast flints produced from misch metalor cerium-iron alloys.

Other alloying components or iillers and methods of manufacture have also been proposed in order Vto produce ilints of low specific gravity. Thus, for example, it

is known to produce a flint by the metallo-ceramic method from magnesium and misch metal powder. Flints produced in this manner, however, have the disadvantage of readily crumbling on account of the difficulty of powder-metallurgical working of the very base starting metals. In addition, they do not attain the pyrophorosity of the cast flints at present on the market.

U.S. Patent 2,660,301 ydisclosed the working of pyrophoric misch metal or cerium-iron alloys with the aid of extrusion presses.

It is to be understood that misch metal is a commercial forrn of cerium and that a cerium-iron alloy generally is manufactured using misch metal, and such cerium-iron alloys are generally actually misch metaliron alloys.

It is therefore an object of the present invention to provide means conducive to the production of int material of reduced speciiic gravity which substantially presents and retains pyrophoric properties of iiints of greater specific gravity.

Another object of the present invention is to provide means affording the production` of a nt of reduced lspeciiic gravity which is distinguished from known ilints by its particular great wear resistance.

It is a further object of the present invention to provide a flint of reduced specific gravity which may be readily worked.

It is a further object of the present invention to provide means contributing to the obtainment of flint alloys of reduced specic gravity having great `strength and resistance to crumbling.

Yet ,vanother object of the present invention is to provide an extruded Hint of reduced speciiic gravity.

Still another object of the present invention resides .in the provision of an extrusion process yielding flint material of reduced specific `gravity and enhanced desirable characteristics, such as wear resistance, sparking effects, and durability.

To this end, according to the present invention, a core of any suitable light-metal or alloy thereof, for example, aluminium, magnesium or alloys thereof, is inserted in a cast billet which is to be extruded, for example, at about 480 to 500 C. at a pressure ranging from 40,000 to 75,000 psi. and which is composed of an extrudable misch metal-iron or cerium-iron alloy containing, for example, about 18 to 22% Fe, about 2% of Mg, about 1% of Sn, the remainder being preferably misch metal. The resultant bimetal ingot is extruded under normal operational conditions. llt has been found that in ,this way it is possible to produce int rods having a sheath length of many meters and containing a light metal core, which is disposed uniformly within and -forming an intimate part of the cross-section of the flint, extends substantially equally overl the entire length of the latter and contributes to a strong anchorage of the core in the sheath and vice versa.

In order to enable theinvention to be more readily understood, reference is made to the accompanying drawings, in which:

Fig. l is a cross-section of a flint rod made in accordance with the invention and shown on an enlarged scale;

Fig. 2 is a longitudinal section of a int rod according to Fig. l;

Fig. 3 is a section through a pressing ingot suitable for the production of iiint material in accordance with the invention and shown on an enlarged scale;

Fig. 4 is a section taken along the line 4 4 of Fig. 3; and

Figs. 5 and 6 are a cross-section and a longitudinal section, respectively, on an enlarged scale of a second embodiment of a flint rod produced in accordance with the invention.

In Figs. l and 2, a denotes a light metal core of approximately circular configuration and surrounded uniformly by .a sheath b of pyrophoric alloy.

It has further been found that the flints of the present invention can be produced by the simultaneous pressing of the bimetal billet or ingot, which thus consists of a cast billet or 1an ingot, hollowed out by machining or any other method, and composed of an extrudable misch metal or cerium-iron alloy into which has been inserted a filler or core oflight metal, e.g. magnesium, aluminium, or an alloy thereof.

This core may be formed by cutting, machining or casting. It has moreover been found that an extrudable bimetal ingot can be obtained directly by casting a pyrophoric alloy around la light metal core.

In carrying out the invention, preferably the extrudabilityof the inserted Vcoreof magnesiumormagnesium alloy is approximately equal to that of the outer ingot of misch metalor cerium-iron. This requirement, which arises from the fact that the .extrusion kprocess for the two metals which are of very different structures must be carried out at the same temperature in one operation, is fullled in the exemplary case where the outer part of `thecombined ingot is composed of a misch metaliron alloy containing 20% of Fe, and where an alloy containing 3% to 6% of Al is used for the magnesium core. Depending upon the composition of the ceriumiron alloy, magnesium alloys of other compositions may also be advantageous. Thus, for example, combinations with cerium and'manganese are possible.

In the second place, the inserted cast core should be shaped in a predetermined manner. Thus, for example, in the pressing of a cast ingot composed of an alloy having good extrusion properties and containing about 18 to 22% of Fe, about 2% of Mg, `about 1% of Sn, remainder being misch metal, and a magnesium core alloy containing about Al, the structure of the combined pressing ingot indicated in Figs. 3 and 4 of the accompanying drawings has given good results. b again denotes the light metal core and a the pyrophoric metal. An ingot a 28 mm. in diameter by 40 mm. length containing an insert of magnesium alloy b of 20 mm. diameter tapering to labout 7 mm. and then to a point, upon extrusion produces a rod of 2.4-3.0 mm. diameter, preferably 2.6 mm., wherein the core b has a diameter of .6 to .8 mm. Thus the-diameter of the core generally ranges in size about 25% the ydiameter of the casing.

If aluminium is used as core material, according to the invention an aluminium alloy containing for example about 4% of Cu and about 1% of Mg should be used. However, it is possible to use also other alloys, provided they comply with the requirements hereinbefore set forth.

Depending upon the extrudability of the light metal core inserted in the pyrophoric ingot, which can be adapted in various ways by special alloy-technical measures to the pressing properties of the outer ingot composed of a pyrophoric misch metal-iron alloy, variations in the form of the bimetal starting ingot are possible. In this way a shape can always be achieved which ensures good and uniform distribution of the light metal core inside the pressed rod of pyrophoric metal.

It is also possible, in order to achieve desirable objects, to provide the starting ingot of ceriurn-iron alloys. with inserts of light metal or light metal alloys in other ways Thus, for example, it has been found that light metal wires inserted in the longitudinal direction of the ingot, and disposed in any ydesired manner and number in the cross-section of the ingot, without however passing out to the side surfaces of the ingot, lead to similar result. A tube inserted in the ingot before pressing, and composed of light metal or a light metal alloy also enables the desired reduction of specific gravity to be achieved. After pressing, pyrophoric metal rods are then obtained, such as those illustrated by way of example in Figs. 5 and 6 in which a again designates the light metal and b the pyrophoric metal.

Further 4experiments have shown that by inserting in the ingot, which is hollowed or pre-shaped by casting, pulverulent pyrophoric substances containing, for example, inter-metallic cerium-magnesium compounds containing more than 40% of Mg, flints having good pyrophoric properties may be obtained by subsequent simultaneous extrusion under otherwise customary conditions. In this method it is advantageous to add to `the pyrophoricV metal powder a Vfiller composed of -an inert, i.e. non-pyrophoric, metal powder of small grain size, for example tin. In this manner it is also possible to produce by extrusion, flints of low speciic gravity having good pyrophoric properties.

The following examples are illustrative of the practice of the present invention:

Example I A int alloy containing about 20% by weight of iron and about by weight of misch metal is cast in the form of a tubular ingot. A rod of magnesium-aluminum alloy containing about 5% by weight 'of aluminum is tightly inserted in the tubular ingot and the ingot is extruded at about 500 C. in a conventional manner. A flint of reduced specic gravity is thereby produced, which flint is characterized by retention of its strength and pyrophorosity.

Example II An alloy containing by weight about 18% of iron, about 2% of magnesium, about 1% of tin, the remainder comprising misch metal is cast into an ingot and hollowed out by machining. A Acast rod of aluminum alloyed with about 4% by weight of copper and about 1% by weight of magnesium is inserted into the hollowed-out or bored ingot and the ingot is thereafter extruded.

The extrusion process serves to integrate the core with the sheath while effecting the requisite reduction in cross section to a commercially useful size. Upon completion the core can no longer be withdrawn from the surrounding int material since an integration even more permanent than bonding has been achieved due to the elects of suicient heat and pressure.V From photomicrographs shown in the drawings it can be readily seen that the line of demarcation between the zones is not sharp and distinct and it therefore appears that' some crystalline association may have occurred along the line of contact, thereby erasing the smooth initial boundary between the core and surrounding ingot. The magnesium alloy core b during extrusion will intimately and mechanically interlock and enmesh with the pyrophoric sheath a, so that they cannot be separated from each other for all practical purposes. The magnesium or magnesium alloy core not only contributes to a int of light weight but is also conducive to increased pyrophoric properties, as core splinters and particles` during int- Wheel operation will enhance the combustion or ignition initiated by thel outer pyrophoric sheath material.

The sheath of pyrophoric flint may be composed of any extrudable alloys such as lthose disclosed in U.S. Patent 2,660,301, which contain varying proportions of iron and misch metal with the possible addition of other alloying constituents. Similarly, the core of light metal may contain alloying constituents, such as copper or other metals. As noted, preferably the extrudability of the core is approximately equal to that of the outer ingot.

Various changes and modifications may be made without departing from the spirit and scope of the present invention and it is intended that such obvious changes and modifications be embraced by the annexed claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

l. A [pyrophoric composition of matter comprising a mass extruded from a bimetal ingot of a cerium-iron alloy containing 20% by weight of iron and having a diameter of 28 mm. and a length of 40 mm., said ceriumiron alloy ingot having embedded therein prior to its extrusion .a magnesium aluminum alloy core containing from 3% to 6% of aluminum and having a diameter of 20 mm. tapering to a diameter of 7 mm. and down to a pointed end.

2. A pyrophoric composition of matter of relatively low specific gravity comprising a hollowed casing extruded from a bimetal ingot of cerium-iron alloy containing about 20% by weight of iron, said casing having embedded therein prior to its extrusion a lightweight alloy core selected from the class of aluminum-magnesium alloy and cerium-magnesium alloy wherein the alloy contains in excess of 40% by Weight of magnesium, the diameter of said core ranging in size about 25% the diameter of said casing.

3. The method of producing a pyrophoric composition of relatively low specific gravity, which comprises the steps of forming a hollowed casing of cerium-iron alloy containing about 20% by Weight of iron, filling said hollowed casting with a core comprising powdered cerilum-magnesium alloy containing in excess of 40% by Weight of magnesium, and thereafter extruding the resultant casing with said lling under heat and pressure to form a solid mass of pyrophoric matter with the diameter of said core ranging in size about 25% the diameter of said casing.

References Cited in the le of this patent UNITED STATES PATENTS 

1. A PYROPHORIC COMPOSITION OF MATTER COMPRISING A MASS EXTRUDED FROM A BIMETAL INGOT OF A CERIUM-IRON ALLOY CONTAINIG 20% BY WEIGHT OF IRON AND HAVING A DIAMETER OF 2.8 MM. AND A LENGTH OF 40 MM. SAID CERIUMIRON ALLOY INGOT HAVING EMBEDED THEREIN PRIOR TO ITS EXTRUSION A MAGNESIUM ALUMINUM ALLOY CORE CONTAINING FROM 3% TO 6% OF ALUMINUM AND HAVING A DIAMETER OF 20 MM. TAPERING TO A DIAMETER OF 7 MM. AND DOWN TO A POINTED END. 